Open-chain polyazaalkanes functionalised with pyrene groups as sensing fluorogenic receptors for metal ions

The new open-chain polyazaalkanes ligands L 1 , L 2 , L 3 and L 4 functionalised with one or two pyrene groups were synthesised and characterised and their potential use as selective cation and anion sensing chemosensors studied. Solution studies by potentiometric methods were carried out in the presence of the metal cations Cu 2+ and Zn 2+ in acetonitrile–water (70:30 v/v, 0.1 mol dm −3 tetrabutylammonium perchlorate, 25 °C) The results are compared with those reported for the analogous non-functionalised ligand triethylentetraamine ( tta ). The fluorescence behaviour of the ligands L 1 –L 4 has been studied as a function of the pH in the presence of the metal cations Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ and Pb 2+ in acetonitrile–water 70:30 v/v mixtures. The Zn 2+ and Cd 2+ cations enhance the fluorescence emission of the L 1 –L 4 chemosensors at basic pH, whereas Cu 2+ induce quenching of the fluorescence emission at acid pH. The fluorescence behaviour of L 1 –L 4 receptors was also studied as a function of the pH in acetonitrile–water 70:30 v/v in the presence of anions.